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Unexpected behavior of the 3 J CH coupling constant in unsaturated compounds
Author(s) -
Couto Uenifer Rodrigues,
NavarroVázquez Armando,
Tormena Cláudio Francisco
Publication year - 2019
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4885
Subject(s) - chemistry , coupling constant , constant (computer programming) , coupling (piping) , computational chemistry , quantum mechanics , physics , mechanical engineering , computer science , engineering , programming language
The experimental and theoretical behavior of the (OC)CCH 3 J CH coupling constant is investigated for a series of α,β‐unsaturated compounds ( 1 to 8 ), and for some of them, the well‐known relationship ( 3 J CHcis < 3 J CHtrans ) was observed. However, for some compounds, close values for 3 J CHcis and 3 J CHtrans couplings were observed, and for aldehydes group containing compounds ( 7 and 8 E ), an inversion order is observed ( 3 J CHcis > 3 J CHtrans ). In all cases where the 3 J CHcis < 3 J CHtrans relationship it is not followed, a polar group or electronegative atom oriented in opposite direction ( s‐trans ) to the HCC hydrogen is present, suggesting that conformational preference of such polar group or atoms are important factor on the behavior of 3 J CH couplings. Taking all of these in consideration, a new Karplus‐type equation was proposed for 3 J CH couplings in α,β‐unsaturated compounds, which can be used for configurational and conformational assignment on trisubstituted double bond derivatives.